﻿<!DOCTYPE html>
<html>
<head>
  <title>Links to Links</title>
  <!-- Copyright 1998-2021 by Northwoods Software Corporation. -->
  <meta name="description" content="Links can connect with Links by using label Nodes on Links." />
  <meta name="viewport" content="width=device-width, initial-scale=1">

  <script src="../release/go.js"></script>
  <script src="../assets/js/goSamples.js"></script>  <!-- this is only for the GoJS Samples framework -->
  <script id="code">
    function init() {
      if (window.goSamples) goSamples();  // init for these samples -- you don't need to call this
      var $ = go.GraphObject.make;

      myDiagram =
        $(go.Diagram, "myDiagramDiv",  // create a Diagram for the DIV HTML element
          {
            "LinkDrawn": maybeChangeLinkCategory,     // these two DiagramEvents call a
            "LinkRelinked": maybeChangeLinkCategory,  // function that is defined below
            "undoManager.isEnabled": true
          });

      // when the document is modified, add a "*" to the title and enable the "Save" button
      myDiagram.addDiagramListener("Modified", function(e) {
        var button = document.getElementById("SaveButton");
        if (button) button.disabled = !myDiagram.isModified;
        var idx = document.title.indexOf("*");
        if (myDiagram.isModified) {
          if (idx < 0) document.title += "*";
        } else {
          if (idx >= 0) document.title = document.title.substr(0, idx);
        }
      });

      // the regular node template, which supports user-drawn links from the main Shape
      myDiagram.nodeTemplate =
        $("Node", "Auto",
          {
            locationSpot: go.Spot.Center,
            layerName: "Background"
          },  // always have regular nodes behind Links
          new go.Binding("location", "loc", go.Point.parse).makeTwoWay(go.Point.stringify),
          $("Shape", "RoundedRectangle",
            {
              fill: "white", stroke: null,
              portId: "", fromLinkable: true, toLinkable: true, cursor: "pointer"
            },
            new go.Binding("fill", "color")),
          $("TextBlock",
            { margin: 8 },  // make some extra space for the shape around the text
            new go.Binding("text", "key"))  // the label shows the node data's key
        );

      // This is the template for a label node on a link: just an Ellipse.
      // This node supports user-drawn links to and from the label node.
      myDiagram.nodeTemplateMap.add("LinkLabel",
        $("Node",
          {
            selectable: false, avoidable: false,
            layerName: "Foreground"
          },  // always have link label nodes in front of Links
          $("Shape", "Ellipse",
            {
              width: 5, height: 5, stroke: null,
              portId: "", fromLinkable: true, toLinkable: true, cursor: "pointer"
            })
        ));

      // the regular link template, a straight blue arrow
      myDiagram.linkTemplate =
        $("Link",
          { relinkableFrom: true, relinkableTo: true, toShortLength: 2 },
          $("Shape", { stroke: "#2E68CC", strokeWidth: 2 }),
          $("Shape", { fill: "#2E68CC", stroke: null, toArrow: "Standard" })
        );

      // This template shows links connecting with label nodes as green and arrow-less.
      myDiagram.linkTemplateMap.add("linkToLink",
        $("Link",
          { relinkableFrom: true, relinkableTo: true },
          $("Shape", { stroke: "#2D9945", strokeWidth: 2 })
        ));


      // GraphLinksModel support for link label nodes requires specifying two properties.
      myDiagram.model =
        $(go.GraphLinksModel,
          { linkLabelKeysProperty: "labelKeys" });

      // Whenever a new Link is drawng by the LinkingTool, it also adds a node data object
      // that acts as the label node for the link, to allow links to be drawn to/from the link.
      myDiagram.toolManager.linkingTool.archetypeLabelNodeData =
        { category: "LinkLabel" };

      // this DiagramEvent handler is called during the linking or relinking transactions
      function maybeChangeLinkCategory(e) {
        var link = e.subject;
        var linktolink = (link.fromNode.isLinkLabel || link.toNode.isLinkLabel);
        e.diagram.model.setCategoryForLinkData(link.data, (linktolink ? "linkToLink" : ""));
      }

      load();
    }

    // Show the diagram's model in JSON format
    function save() {
      document.getElementById("mySavedModel").value = myDiagram.model.toJson();
      myDiagram.isModified = false;
    }
    function load() {
      myDiagram.model = go.Model.fromJson(document.getElementById("mySavedModel").value);
    }
  </script>
</head>
<body onload="init()">
  <div id="sample">
    <div id="myDiagramDiv" style="border: solid 1px black; width:100%; height:400px;"></div>
    <p>
      This demonstrates the ability for a <a>Link</a> to appear to connect with another Link.
      Regular links are blue.  Link-connecting links are green.
      Try moving a node around to see how the links adapt.
      Initially the "Alpha" node connects with the link between Gamma and Delta.
      There is also a link between the two horizontal links.
    </p>
    <p>
      This effect is achieved by using "label nodes" that belong to links.
      Such "label nodes" are real <a>Node</a>s that are referenced from their owning <a>Link</a>.
      This sample customizes the "Link Label" Node template to allow the user to draw new links to/from such label nodes.
    </p>
    <p>
      Newly drawn links automatically get a label node by the <a>LinkingTool</a> because this sample initializes
      the <a>LinkingTool.archetypeLabelNodeData</a> property of the <a>ToolManager.linkingTool</a>.
      The category (i.e. template) of each link is determined by what kinds of nodes the link is connected with.
    </p>
    <div>
      <div>
        <button id="SaveButton" onclick="save()">Save</button>
        <button onclick="load()">Load</button>
        Diagram.model saved in JSON format:<br />
      </div>
      <textarea id="mySavedModel" style="width:100%;height:400px">
{ "class": "go.GraphLinksModel",
  "linkLabelKeysProperty": "labelKeys",
  "nodeDataArray": [
{"key":"Alpha", "color":"lightblue", "loc":"29 14"},
{"key":"Beta", "color":"orange", "loc":"129 14"},
{"key":"Gamma", "color":"lightgreen", "loc":"29 106"},
{"key":"Delta", "color":"pink", "loc":"129 106"},
{"key":"A-B", "category":"LinkLabel" },
{"key":"G-D", "category":"LinkLabel" },
{"key":"A-G", "category":"LinkLabel" },
{"key":"A-G-D", "category":"LinkLabel" },
{"key":"A-B-G-D", "category":"LinkLabel" }
 ],
  "linkDataArray": [
{"from":"Alpha", "to":"Beta", "labelKeys":[ "A-B" ]},
{"from":"Gamma", "to":"Delta", "labelKeys":[ "G-D" ]},
{"from":"Alpha", "to":"Gamma", "labelKeys":[ "A-G" ]},
{"from":"Alpha", "to":"G-D", "labelKeys":[ "A-G-D" ], "category":"linkToLink"},
{"from":"A-B", "to":"G-D", "labelKeys":[ "A-B-G-D" ], "category":"linkToLink"}
 ]}
      </textarea>
    </div>
  </div>
</body>
</html>
